Conventionally, a heat dissipating body such as a heat sink is widely used for many of heat-generating electronic components in order to prevent damage, performance degradation and the like due to an increase in temperature during use. For efficient conduction of the heat generated from the heat-generating electronic component to the heat dissipating body, a heat conductive material is used between the heat-generating electronic component and the heat dissipating body.
It is known to use a heat dissipating sheet or a heat dissipating grease for the heat conductive material. Generally, heat dissipating grease has properties similar to a liquid, and compared to heat dissipating sheets, can adhere tightly to the heat-generating electronic component and the heat dissipating body to decrease interfacial thermal resistance without being influenced by surface irregularities of the heat-generating electronic component and the heat dissipating body. However, the heat dissipating grease tends to bleed oil component when used for an extended period.
For example, Patent Reference 1 proposes a heat dissipating silicone grease having a heat conductive filler contained in a base oil of a particular polyorganosiloxane. Patent Reference 2 proposes a heat dissipating material which contains polyorganosiloxane having a vinyl group bonded to a silicon atom, polyorganohydrogensiloxane having a hydrogen atom bonded to a silicon atom and a heat conductive filler, and is gelated by a cross-linking reaction in the presence of a platinum based catalyst.
It is generally known that such a conventional heat dissipating material has the heat conduction performance improved by high filling of the heat conductive filler. However, since the conventional heat dissipating material tends to cause lowering of workability in the production process, the upper limit of its blending amount is restricted. Therefore, due to the further increase in heat generation resulting from recent trends of higher densities and performance of heat-generating electronic components, a sufficient heat conduction effect cannot be obtained by the conventional heat dissipating material. Furthermore, oil bleeding is not reduced sufficiently, allowing free oil component to bleed from a gel-like cured material due to external pressures such as swaging or the like, and electronic parts are easily contaminated. The contamination tends to prevent the achievement of the original performance of the electronic parts or to cause them to operate poorly.
Patent Reference 1: JP-A 2003-301189 (KOKAI)
Patent Reference 2: JP-A 2002-294269 (KOKAI)